Various remote monitoring and control systems have been suggested using time division multiplex transmissions which include interruption processing techniques.
U.S. Pat. No. 4,586,040 (Akiba et al.), issued on Apr. 29, 1986, discloses a interruption handling system in a TDMA remote control system. The TDMA remote control system comprises a plurality of terminals connected to a central controller through a signal line. The format for a transmission signal from the central controller includes a interruption request signal stand-by period "RW" when the central controller accepts interruption request reply signals from the terminals. The terminals are formed into separate sets of terminals, each set having a group identifying information. In a terminal, the interruption request signal identifying the terminal in the group is transmitted during this stand-by period. The stand-by period is divided into a plurality of subperiods corresponding to the group identifying information for a group of terminals to which the terminal belongs to. The individual identifying information sent out as a reply signal is coded information of a plurality of bit wherein the signal of a single bit is represented by a combination of one pulse having a longer pulse width and another pulse having a shorter pulse width, or vice versa. The central controller detects the combination of two pulses having a longer pulse width in each bit of the individual identifying information and thereby can detect that there exists in a single group of terminals more than two terminals sending out interruption request signals. Possible addresses are evaluated based on the bit position(s) where such combination(s) are detected so that only the terminals corresponding to the possible addresses can be polled.
U.S. Pat. No. 5,144,295 (Nakagawa et al.), issued on Sep. 1, 1992, discloses an interruption processing system in a TDMA transmission system. The system comprises a central control unit interconnected by a pair of signal lines to a plurality of monitoring terminal units and a plurality of controlling terminal units, where each of the terminal units has a specific address. A transmission signal "VS" is transmitted from the central control unit to the respective terminals, and a signal "Vb" is selectively returned from a terminal. The interruption processing system from one of the monitoring units returns to the central control unit a signal which specifies in part of a 4-bit address which group that terminal unit is in (one of four groups of four terminal units each). Such notification of which group the terminal is in is provided to the central control unit by one or more current mode pulse signals within one of four periods within a designated Start (ST) pulse period. Such transmission of current mode pulses identifies the group which contain the interruption request terminal and avoids the need for the central control unit to access all terminal units, so that the specifying operation of the interruption requesting terminal can be attained extremely quickly.
U.S. Pat. No. 4,604,618 (Akiba et al.), issued on Aug. 5, 1986, discloses a TDMA transmission system comprising a host machine 3 and a plurality of addressable terminals connected together by a signal line. The terminals are grouped in sets with each set having a same address. Each of the terminals in a set includes selection switches associated with separate objects to be monitored for selecting one of reply blocks at which a reply signal associated with that object is sent to the host machine. Each terminal of a set has its selections switches set to select a different one of the reply blocks in a reply signal so that no data from the terminals overlaps. In this manner, the host machine can interrogate a set of terminals by sending out a single address, and the data returned from the set of addressed terminals is dependent upon which of the selection switches is turned "ON". The host machine has a record of which reply blocks belong to which terminal of the set of terminals with the same address and the object in that terminal that is being monitored. It thereby can supervise the objects to be monitored in each set of terminals of the system by sending out the address associated with each separate set of terminals.
It is desirable to provide a technique which permits interrupt request transmissions between a plurality of devices or shelves and a single microprocessor that identifies by an encoded interrupt data signal precisely what device or what device or port on a shelf is requesting an interrupt using time division multiplexing and a minimal amount of leads. This avoids the necessity of a microprocessor having to subsequently determine which device or element on a shelf is requesting an interruption once an interrupt request is received.